DE102011054050B4 - Electrical connection material between conductors and its use in a solar cell module - Google Patents

Abstract

An electrical connection material between conductors, comprising 40% by weight to 80% by weight of a urethane-modified acrylate resin, the connection material comprising a polymer binding resin, a radical polymerizable compound, organic peroxide, and a conductive particle, the polymer binding resin a urethane-modified acrylate resin and at least one copolymer selected from an acrylonitrile-butadiene copolymer, an ethyl vinyl acetate copolymer and an acrylic copolymer, and wherein the connecting material has a tensile elongation of 100% to% 500% after curing; and- has a yield strength of ≥10% to ≤50% in a stress-strain diagram, and / or- has a modulus of elasticity of ≥10 MPa to ≤500 MPa at 25 ° C.

Description

Field of invention

The present invention relates to an electrical connection material between conductors including a conductive film or paste, and to a solar cell having a connection structure using the electrical connection material.

Description of relevant technology

In a manufacturing process of a crystalline solar cell module, a conductive cable according to a tape is used for serially connecting cells, in which electrodes for taking electric current are arranged on a silicon substrate, which generate electricity using incident light. For the conductive cable, an angular copper cable immersed in solder or clad with solder is generally used. The current-collecting electrodes (generally silver), which are worked on the solder substrate, are thermally pressed and soldered, whereby the multitude of cells are connected in series ( 1a and 1b represent a cell structure, and 2 illustrates a structure of cells connected in series using the tape).

Generally cells that are ≥12 cm to ≤16 cm square in size are connected by the tape. Since the silicone used for the cells has a linear expansion coefficient of 2.4 ppm / ° C which is different from a linear expansion coefficient of 16.8 ppm / ° C of copper as a main component of the tape, and the joint at 200 ° C or more occurs, stress occurs toward an end point at 183 ° C or less, which is the melting point of the solder depending on the joint length. Such stress causes the cells to bend or break after connection. In addition, in the cyclic heating and cooling test, the connected part will be separated or the cells will be broken.

In order to prevent such problems, methods of joining a tape and a current collecting electrode using a joining material constituted by finely divided conductive particles in a thermally fixed adhesive film have been researched. Since thermally set adhesive adhesives have a lower modulus of elasticity than solder and a lower glass transition temperature (Tg) than the melting point of the solder, the adhesive adhesive is controllable and can therefore be used advantageously for stress relief. Since the adhesive film comprises thermally fixed organic materials, thermal pressing is carried out to connect the tape and the current-collecting electrode ( 3a , 3b and 4th represent a connection structure using the solder connection and the adhesive film).

Since the production of solar cells is expected to increase extraordinarily, there is a need to decrease the time consumed for bonding when using such an adhesive film.

In view of the reliability of connection, an adhesive film containing epoxy resin as a main component has high performance in electrical applications. However, conductive adhesive epoxy films used for flat panel displays (FPDs) and having microencapsulated imidazoles dispersed therein require a bonding time of 10 seconds. When a conductive adhesive film mainly containing acrylate or methacrylate having a vinyl group or the like is used, the connection time may be 5 seconds or less, although the reliability of the connection is not guaranteed. Currently commercially available joining materials have a joining time of 5 seconds or less, especially 3 seconds, while joining materials which have both a satisfactory joining time and an excellent joining are yet to be developed. Methods of dispersing conductive and metallic particles in an adhesive adhesive as a bonding material for a current collecting electrode of a solar cell and a tape are known, for example, from documents such as Japanese Unexamined Patent Publication JP 2009 - 283 606 A of Japanese patent application JP H05 293 727 A and Japanese Unexamined Patent Publication JP 2008 - 300 403 A disclosed.

The US 2003/0 008 934 A1 describes an electrically conductive coating composition that functions as a seal / primer comprising (a) a radiation curable polymerizable compound, (b) a photoinitiator, and (c) a conductive pigment.

The US 2010/0148 130 A1 describes a composition for a circuit connection film and a circuit connection film using the same, the composition containing a binder resin including an acrylate-modified urethane resin, a carboxyl-modified acrylonitrile-butadiene rubber and an acrylic copolymer, the acrylic copolymer having an acid value of 1 to 100 mg KOH / g and a radical polymerizable compound which contains at least one isocyanurate acrylate compound and a compound having a (meth) acrylate group and an organic peroxide.

Summary of the invention

• - eine Streckgrenzbelastung von ≥10% bis ≤50% in einem Spannungsdehnungsdiagramm, und/oder
• - ein Elastizitätsmodul von ≥10 MPa bis ≤500 MPa bei 25°C aufweist, zur Verfügung gestellt.

In one aspect of the present invention, an electrical connection material between conductors, comprising 40 40% by weight to 80% by weight of a urethane-modified acrylate resin, the connection material being a polymer binding resin, a free-radically polymerizable compound, organic peroxide, and a having conductive particles, wherein the polymer binding resin comprises a urethane-modified acrylate resin and at least one copolymer selected from an acrylonitrile-butadiene copolymer, an ethyl vinyl acetate copolymer and an acrylic copolymer, and wherein the connecting material after curing has a tensile elongation of ≥100% to ≤ 500%; and

• - a yield point load of ≥10% to ≤50% in a stress-strain diagram, and / or
• - has a modulus of elasticity of ≥10 MPa to ≤500 MPa at 25 ° C.

Another aspect of the present invention is directed to the use of the electrical connection material in a solar cell module.

Exemplary embodiments also provide a solar cell module that has a plurality of solar cells that are connected to one another via a connection structure. The connection structure includes at least one electrode on a surface of each solar cell, a conductive wire connected to the electrodes on the plurality of solar cells, and an electrical connection material between the conductive wire and each of the electrodes. The electrical connection material comprises 40% by weight to 80% by weight of a urethane-modified acrylate resin, based on a total weight of the electrical connection material, and after curing has a tensile elongation of 100% to 500% and a yield strength of ≥ 10% to ≤ 50% in a stress-strain diagram.

Figure list

• 1a shows a schematic representation of a structure of a light-receiving surface of a solar cell;
• 1b shows a schematic representation of a structure from a rear side of a solar cell;
• 2 Fig. 3 is a schematic diagram showing the connection between a solar cell and a tape;
• 3 shows a schematic representation of a connection structure between the solar cell and the band by means of an electrical connection material according to one of the exemplary embodiments;
• 4th Figure 11 illustrates a construction of a pattern made in accordance with an exemplary embodiment of the present invention;
• 5 shows a stress-strain diagram showing measurement results from a strain test; and
• 6th Figure 13 is a schematic diagram illustrating a method of measuring resistance using a pattern in accordance with the exemplary embodiment of the present invention.

Detailed description of the invention

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

Referring to 1a , can be a solar cell 21 first, front current collecting electrodes 11 , ie finger leads, and secondly, front conductive electrodes 12th , ie busbars, on a light-collecting surface, ie on the front side, of a carrier material 13th the solar cell 21 , lock in. A back of the solar cell 21 , as in 1b shown can be a rear electrode 14th , e.g. a Aluminum electrode, and rear current collecting electrodes 15th on the carrier material 13th , include. The carrier material 13th can be, for example, a polycrystalline silicon layer or wafer. As in 2 shown, can use a variety of solar cells 21 via a conductive wire 22nd , ie a tape 22nd to be connected to each other. The conductive wire 22nd , for example a copper wire, may be connected to the current collecting electrodes, as detailed below with reference to FIG 3 is described. The conductive wire 22nd , for example an angular copper wire dipped in solder or coated with solder, can for example be thermally pressed or soldered along the current-conducting electrodes, the plurality of solar cells 21 can be connected in series. For example, any solar cell can 21 have a size of 12 cm ² to 16 cm ² .

As in 3 Shown can be any conductive wire 22nd with the conductive electrode, ie the second front current collecting electrodes 12th and / or rear-side current-collecting electrodes 15th , via an electrical connection material 35 be connected. For example, it can be a conductive wire 22nd cover an associated electrically conductive electrode completely, so that the electrical connection material 35 in between, that is, in direct contact with each of the conductive wires 22nd and the conductive electrode. The solar cell 21 may, for example, have a square shape with a size of 16 cm ² , and the conductive wire 22nd can with the electrically conductive electrode over a connection length of 15 cm with the electrical connection material 35 be connected in between.

The electrical connection material 35 may for example be distributed up to a thickness of 35 µm followed by placement on a heating press. On the electrical connection material 35 For example, a silicone rubber having a thickness of 0.2 mm may be arranged, followed by thermal pressing at 190 ° C and 30 MPa for 15 minutes to cure the electrical connection material 35 to a hardened film, that is, layer.

Regarding 1a to 4th assuming that a conductive electrode on a cell and a tape with a copper core are connected to each other over a length of 15 cm, there is a difference of 14.4 × 10-6 / K in the linear expansion coefficient between a silicon wafer (2, 4 × 10-6 / K) and the tape core (16.8 × 10-6 / K). Provided that the conductive electrode and the tape are connected at 200 ° C with a solder paste placed around the tape and the connected tape contracts evenly from the center point from 200 ° C to room temperature, deformation at an end portion of the Tape of 14.4 × 10 ^-6 / K × (200 ° C-25 ° C) × 75mm = 0.189 mm.

Such deformation leads to significant curvature of the cell and possible breakage of the same. When a solder with a melting point of 183 ° C is used, the stress occurs at the melting point or below, and the deformation, which affects the degree of stress, decreases accordingly. When an organic adhesive is used, the stress occurs at a temperature of Tg or less, and hence the deformation can be further reduced by regulating Tg. It is also effective to reduce the elastic modulus of an adhesive adhesive to relieve theoretical stress using adhesive components. That is, stress resulting from the deformation between the cell and the tape can be decreased by lowering the elastic modulus of the adhesive adhesive to reduce Tg. Nevertheless, the adhesive components must be mixed in order to guarantee the reliability and balance of the properties, since such structures of the adhesive could lead to the decrease in the reliability.

The inventors of the present invention produced a connecting material which had a tensile elongation of 100% or more, preferably 100% to 500%, particularly preferably 200 to 300%, a yield point load of 10% or more, preferably 10 to ≤50% in a stress-strain diagram, and a modulus of elasticity of ≥10 to ≤500 MPa, preferably ≥30 to ≤450 MPa at 25 ° C after curing, whereby a connection between the electrically conductive electrode on the cell and the tape within 5 seconds is made possible and excellent reliability is achieved. For curing, the joining material with a thickness of 35 µm is placed on a heating press and a silicone rubber with a thickness of 0.2 mm is spread thereon, followed by thermal pressing at 190 ° C and 30 MPa for 15 minutes to cure the joining film.

The connecting material for electrical connection between conductors having these properties may contain a polymer bonding resin, a radical polymerizable compound, an organic peroxide, and a conductive particle.

The connecting material for the electrical connection between conductors can be 70% by weight to 85% by weight of the polymer binding resin, 13% by weight to 20% by weight of the free-radically polymerizable Compound,> 1% by weight to 5% by weight of the organic peroxide, and 1% by weight to 5% by weight of the conductive particle.

Polymer binding resin

The polymer binding resin forms a binder component which acts as a matrix for forming a conductive film and which may include, but are not limited to, typical thermoplastic resins.

For example, the polymer binder resin contains at least one selected from the group consisting of acrylonitrile, styrene-acrylonitrile, methyl methacrylate-butadiene-styrene, butadiene, acrylic, urethane, epoxy, phenoxide, polyamide, olefin, polyester, silicone resins, and combinations thereof. In particular, the connecting material can contain a urethane-modified acrylate resin as the polymer binder resin.

The urethane-modified acrylate resin can be present in the electrical connection material in an amount of 40% by weight to 80% by weight. Appropriate film properties and improved reliability can be achieved within this range. The urethane-modified acrylate resin in particular can be used in an amount ≥ 50% by weight to 70% by weight. are present.

The urethane-modified acrylate resin enables the bonding material to have a low glass transition temperature and thereby improves the flowability, whereby it has high adhesion due to the presence of a urethane group in a molecular chain. In particular, when the urethane-modified acrylate resin is used for the conductive film, the curing result is improved and the temperature decreases in a joining process.

The urethane-modified acrylate resin contains diisocyanate, polyol, diol, and acrylate components. The diisocyanate can contain aromatic, aliphatic, and alicyclic diisocyanates, or mixtures thereof. The polyol may contain polyester, polyol, polyether polyol, polycarbonate polyol, and the like, which have at least two hydroxyl groups in a molecular chain. The diol can include 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, and the like. The acrylate can contain components obtained by polymerizing hydroxyl (meth) acrylate or amine (meth) acrylate. The urethane-modified acrylate resin containing these four components is provided by polyaddition such that the molar ratio of isocyanate group (NCO) to hydroxyl group (OH) ≥1.04 to ≤1.6 and the polyol content ≤70% or less below three Components other than the acrylate, followed by the reaction of a terminal functional group of the urethane produced by polyaddition reaction, that is, an isocyanate group with hydroxyl (meth) acrylate or amine (meth) acrylate in a molar ratio of ≥0.1 to ≤ 2.1. In addition, the remaining isocyanate groups are subjected to a reaction with alcohols, whereby the urethane-modified acrylate resin is produced. The polyaddition here can be carried out using any typical method from the prior art. Moreover, the polyaddition can be carried out at a temperature of 90 ° C. and a pressure of 1 atm for five hours using, but not limited to, a tin-based catalyst.

In addition to the above urethane-modified acrylate resin, thermoplastic resins such as an acrylonitrile-butadiene copolymer, an ethylene-vinyl acetate copolymer and an acrylic copolymer can be used as a mixture for the binder resin that forms the connecting material.

Any acrylonitrile butadiene copolymer and any ethylene-vinyl acetate copolymer known in the art can be used. Commercially available examples of the acrylonitrile-butadiene copolymer are 1072CGX, NX775, or the like (Zeon Chemicals), and commercially available examples of the ethylene-vinyl acetate copolymer are EVA 700, EVA 800, and the like (Byer).

The acrylic copolymer which can be used as a polymer binder resin can contain acrylic copolymers obtained by polymerizing acrylic monomers such as ethyl, methyl, propyl, butyl, hexyl, octyl, dodecyl and lauryl (meth) acrylates, modifications thereof such as acrylates, acrylic acids, methacrylic acids , Methyl methacrylates and vinyl acetates, and modifications thereof, for example acrylic monomers, can be obtained without being limited thereto. The acrylic copolymer can have a glass transition temperature (Tg) of ≥50 ° C to ≤120 ° C.

The acrylic copolymer mainly contains a hydroxyl or carboxyl group to have an acidity of ≥1 mgKOH / g to ≤100 mgKOH / g, and further optionally contains an epoxy or alkyl group. If the glass transition temperature of the acrylic copolymer is less than 50 ° C, the film becomes soft, resulting in poor compressibility and decreasing reliability of bonding with urethane acrylate, which has a low Tg. If the glass transition temperature is higher than 120 ° C, the film will crack and not be properly formed. Furthermore, if the acidity of the acrylic copolymer is less than 1 mgKOH / g, satisfactory adhesion cannot be obtained. If the acidity exceeds 100 mgKOH / g, the reliability of the connection may be lowered due to corrosion.

Specifically, the acrylic copolymer can have a glass transition temperature of 90 ° C to achieve stable film properties and it can have an acidity of 3.4 mgKOH / g to act as a binder. Since the urethane binder has a relatively low glass transition temperature, since the acrylic copolymer mixed therewith as a binder has a higher glass transition temperature, the reliability of the connection increases favorably. However, if the acrylic copolymer has a glass transition temperature that is too high, it is easily broken, so that the film is not properly formed.

The polymer bonding resin can be present in the bonding material in an amount of 70% by weight to 85% by weight. Within this range, in a process for dispersing the conductive particle, sufficient dispersibility can be secured and excellent flowability can be achieved to obtain a stable connection state. In particular, the polymer binding resin can be present in an amount of 75% by weight to 85% by weight.

The urethane-modified acrylate resin can be present in the polymer binding resin in an amount of 60 60% by weight to 90% by weight. Excellent adhesion and high reliability of the connection can be achieved within this framework. Specifically, the urethane-modified acrylate resin can be present in an amount of 75% by weight to 90% by weight.

At least one copolymer selected from acrylonitrile-butadiene copolymer, ethylene-vinyl acetate copolymer and acrylic copolymer can be present in the polymer binding resin in an amount of 10 to 40% by weight. Within this range, excellent reworkability can be obtained after pressurization in a pressing process, and the film does not separate when it is pressurized. The copolymer can specifically be present in an amount of 10% by weight to 25% by weight.

Radically polymerizable compound

The radical polymerizable compound is a component of a curing agent which functions to ensure the adhesion and reliability of the bond between the bonded layers when the radical curing reaction occurs.

The radical polymerizable compound of the connecting material is a radical polymerizable compound which has at least one vinyl group and contains at least one selected from a (meth) acrylate oligomer, a (meth) acrylate monomer, and mixtures thereof.

Any (meth) acrylate oligomer can be used as the (meth) acrylate oligomer, for example urethane (meth) acrylates, epoxy (meth) acrylates, polyester (meth) acrylates, fluorine (meth) acrylates, fluorene (meth) acrylates, silicone (meth) acrylates , Phosphorus (meth) acrylates, maleimide-modified (meth) acrylates, and acrylate (methacrylates), which have an average molecular weight in the range from ≥1,000 g / mol to ≤100,000 g / mol.

Specifically, the urethane (meth) acrylate oligomer can contain molecules with an intermediate structure consisting of polyester polyol, polyether polyol, polycarbonate polyol, polycaprolactone polyol, a ring-opened tetrahydrofuran-propylene oxide copolymer, polybutadiene diol, polydimethylsiloxane diol, ethylene glycol, 1,5-butylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, bisphenol A, hydrogenated bisphenol A, 2,4-toluene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 1,5-naphthalene diisocyanate, 1,6-hexane diisocyanate , Isophorone diisocyanate, and bisphenol A propylene oxide are synthesized. The epoxy (meth) acrylate oligomer can contain molecules with an intermediate structure selected from the group consisting of 2-bromohydroquinone, resorcinol, catechic acid, bisphenols, such as bisphenol-A, bisphenol-F, bisphenol-AD and bisphenol-S, 4,4 ' -Dihydroxybiphenyl and bis (4-hydroxyphenyl) ethers; and a (meth) acrylate oligomer which has alkyl, aryl, methylol, allyl, cycloaliphatic, halogen (tetrabromobisphenol A), or nitro groups. In addition, the (meth) acrylate oligomer can contain compounds that contain at least two maleimide groups in the molecule, e.g. 1-methyl-2,4-bismaleimidbenzene, N, N'-m-phenylbismaleimide, N, N'-p-phenylbismaleimide, N, N'-m-tolylenebismaleimide, N, N'-4,4-biphenylbismaleimide, N, N'-4,4- (3,3'-dimethylbiphenyl) bismaleimide, N, N'-4,4- (3.3 '- dimethyldiphenylmethane) bismaleimide, N, N'-4,4- (3,3'-diethyldiphenylmethane) bismaleimide, N, N'-4,4-diphenylmethane bismaleimide, N, N'-4,4-diphenylpropane bismaleimide, N, N'- 4,4-diphenylether bismaleimide, N, N'-3,3'-diphenylsulfonbismaleimide, 2,2-bis [4- (4-maleimidophenoxy) phenyl] propane, 2,2-bis [3-s-buty1-4-8 (4-maleimidophenoxy) phenyl] propane, 1,1-bis [4- (4-maleimidophenoxy) phenyl] decane, 4,4'-cyclohexylidene-bis [1- (4-maleimidophenoxy) -2-cyclohexyl] benzene, 2 , 2-bis [4- (4-maleimidophenoxy) phenyl) hexafluoropropane, etc.

As the (meth) acrylate monomer, any (meth) acrylate monomer can be used, for example, 1,6-hexanediol mono (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (metha) acrylate, 2-hydroxy-3-phenyloxypropyl (meth) acrylate, 1,4-butanediol (meth) acrylate, 2-hydroxyalkyl (meth) acryloyl phosphate, 4-hydroxycyclohexyl (meth) acrylate, neopentyl glycol mono (meth) acrylate, trimethylolethane di ( meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol hexa (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerol di (meth) acrylate, t-hydrofurfuryl ( meth) acrylate, isodecyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, 2-phenoxyethyl (meth) acrylate, isobornyl (meth) acrylate, tridecyl (meth) acrylate, ethoxylated nonylphenol (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, t-ethylene glycol ol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, ethoxylated bisphenol-A di (meth) acrylate, cyclohexanedimethanol di (meth) acrylate, phenoxy -t-glycol (meth) acrylate, 2-methacryloyloxyethyl phosphate, dimethylol tricyclodecane di (meth) acrylate, trimethylol propane benzoate acrylate, fluorene (meth) acrylate, acid phosphoxyethyl methacrylate, etc.

The free-radically polymerizable compound can be present in the compound material in an amount of 13% by weight to 20% by weight. Within this range, excellent reliability and extensive flowability can be ensured after a pressing operation, so that the volume resistance does not increase. The free-radically polymerizable compound can specifically be present in an amount of 13 to 18% by weight.

Organic peroxide

The organic peroxide is a polymerization initiator that acts as a curing agent to generate free radicals when heated or exposed to light.

The organic peroxide can include, but is not limited to, ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, and peroxycarbonates. The organic peroxides can be used as mixtures in terms of contact temperature and time, and storage stability.

Examples of organic peroxides can specifically, but not be limited to, t-butyl peroxylaurate, 1,1,3,3-t-methylbutylperoxy-2-ethylhexanonate, 2,5-dimethyl-2,5-di (2-ethylhexanoyl peroxy) hexane, 1-cyclohexyl-1-methylethyl-peroxy-2-ethylhexanonate, 2,5-dimethyl-2,5-di (m-toluoylperoxy) hexane, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, t-butyl peroxyacetate, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, t-butylcumyl peroxide, t-hexyl peroxyneodecanoate, t-hexylperoxy-2-ethylhexanonate, t-butylperoxy-2 -2-ethylhexanonate, t-butylperoxyisobutyrate, 1,1-bis (t-butylperoxy) cyclohexane, t-hexyl peroxyisopropylmonocarbonate, t-butylperoxy-3,5,5-trimethylhexanonate, t-butylperoxypivalate, cumylperoxy-neodecanoate, diisopropylbenzene hydroperoxide, , Isobutyl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, amber peroxide, benzoyl peroxide, 3,5,5-trimet ethylhexanoyl peroxide, benzoyl peroxytoluene, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, di-n-propyl peroxydicarbonate, diisopropyl peroxycarbonate, bis (4-t-butylperoxydicarbonate, di-ethoxy-2-oxydicarbonate, di-ethoxy-2-carboncyclohexyl) ethylhexylperoxy) dicarbonate, dimethoxybutylperoxydicarbonate, di (3-methyl-3-methoxybutylperoxy) dicarbonate, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1 , 1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 1,1- (t-butylperoxy) cyclododecane, 2,2-bis (t-butylperoxy) decane, t-butyltrimethylsilyl peroxide, bis (t-butyl ) dimethylsilyl peroxide, t-butyltriallylsilyl peroxide, bis (t-butyl) diallylsilyl peroxide, and tris (t-butyl) allylsilyl peroxide.

A compound with a half-life temperature of ≥40 ° C to ≤100 ° C within ≥5 hours to ≤15 hours can be used as the organic peroxide. If the half-life temperature of the organic peroxide is too low, its decomposition is rapid, resulting in difficulty in storage at room temperature. If the half-life temperature is excessively large, the rate of polymerization becomes too slow, which is not suitable for rapid curing.

The organic peroxide can be present in an amount range in which there is a balance between the curing properties and the storage of the adhesive, which is 1% by weight to 5% by weight of the connecting material. No bubbles appear within this area. The organic peroxide can be present in an amount from 1% by weight to 3% by weight.

Conducting particle

The electrical connection material between the conductors comprising the above components may contain a conductive particle.

The conductive particle is used as a filler to impart conductivity to the composition for a conductive film.

The conductive particle includes, but is not limited to, metal particles known in the art such as Ni, Pd, Cu, Ag, Al, Ti, Cr, and mixtures thereof. The conductive particle is made by coating non-conductive particles with the aforementioned metal particles and the like.

The conductive particle can have a size of 2 µm to 30 µm depending on the electrodes used and purposes. The conductive particle can be present in the connection material in an amount of 1% by weight to 5% by weight. No defective connection occurs in a connection process within this range. In particular, the conductive particle is present in an amount of 1% by weight to 4% by weight.

Other components

The electrical connection material between conductors according to the present invention may further contain a pigment for coloring, a dye, a polymerization inhibitor, a silane coupling agent, or the like in view of the properties or processability of a product in order to achieve the desired properties of the cured product. These components can be contained in an amount known from the prior art.

The present invention provides an electrical connection material between conductors which has the following properties after curing: a tensile elongation of ≥ 100% or more, a yield stress of oder 10% or more in a stress strain diagram, and a Young's modulus of 10 MPa to 500 MPa at 25 ° C, and the material can be realized as a conductive film or paste for a semiconductor device. In the conductive film, the thickness can be 1 µm to 50 µm.

The material is well suited for the serial connection of cells of a semiconductor solar cell module, for connection of an FPD module, for connection of a COF comprising an IC driver on a polyimide substrate with a glass substrate, a glass epoxy substrate or another plastic substrate, or the like. Meanwhile, one of the conductors to be connected using the material may be surface-treated with at least one of copper, stainless copper or tin, solder, silver and nickel.

The conductive film can be formed by any device or equipment known in the art. The conductive film can be molded by the following process. A binding resin is dissolved and liquefied in an organic solvent, and then the remaining components are added and stirred for a predetermined time. The product is applied to a release film to a thickness of ≥10 µm to ≤50 µm and dried for a predetermined time to volatilize the organic solvent, thereby producing a conductive film having a single-layer structure. Any organic solvent from the prior art can be used for this purpose. Thereafter, the aforementioned process can be repeated at least twice, thereby forming a conductive film having a multilayer structure, e.g. B. at least two layers is produced.

A solar cell of the present invention may have a connection structure using the connection material.

In the following, the present invention will be described in detail with reference to Examples and Comparative Examples. However, it should be noted that these examples are illustrative only and do not limit the scope of the invention.

• 1. Urethan-modifiziertes Acrylatharz 1: Synthetisiert unter Verwendung von 60 Gew.-% Polyol (Polytetramethylenglycol), 39,97 Gew.-% von drei Komponenten enthaltend 1,4-Butandiol, Toluendiisocyanat und Hydroxyethylmethacrylat, und 0,03 Gew.-% Dibutylzinndilaurat als einen Katalysator. Zunächst werden Polyol, 1,4-Butandiol, und Toluendiisocyanat reagiert, um ein Isocyanat-terminiertes Prepolymer zu synthetisieren. Das Isocyanat-terminierte Prepolymer wurde weiter mit Hydroxyethylmethacrylat reagiert, um ein Polyurethanacrylatharz herzustellen, so dass das Molverhältnis von Hydroxyethylmethacrylat/Isocyanat-terminiertes Prepolymer 0,5 ergab. Die Reaktion wurde durch Polyaddition bei 90°C und einem Druck von 1 atm für 5 Stunden in Anwesenheit von Dibutylzinndilaurat als einem Katalysator durchgeführt, wodurch Polyurethanacrylat mit einem mittleren Molekulargewicht von 25.000 g/Mol synthetisiert wurde.
• 2. Urethan-modifiziertes Acrylatharz 2: Synthetisiert unter Verwendung von 60 Gew.-% Polyol (Polytetramethylenglycol), 39,97 Gew.-% von drei Komponenten enthaltend 1,4-Butandiol, Toluendiisocyanat und Hydroxyethylmethacrylat, und 0,03 Gew.-% Dibutylzinndilaurat als einen Katalysator. Zunächst werden Polyol, 1,4-Butandiol, und Toluendiisocyanat reagiert, um ein Isocyanat-terminiertes Prepolymer zu synthetisieren. Das Isocyanat-terminierte Prepolymer wurde weiter mit Hydroxyethylmethacrylat reagiert, um ein Polyurethanacrylatharz herzustellen, wobei das Molverhältnis von Hydroxyethylmethacrylat/Isocyanat-terminiertes Prepolymer 1 war. Die Reaktion wurde durch Polyaddition bei 90°C und einem Druck von 1 atm für 5 Stunden in Anwesenheit von Dibutylzinndilaurat als einem Katalysator durchgeführt, wodurch Polyurethanacrylat mit einem mittleren Molekulargewicht von 28.000 g/Mol synthetisiert wurde.
• 3. Thermoplastisches Harz 1: Acrylonitrilbutadiencopolymer (1072CGX, Zeon Chemicals) gelöst in Toluen/Methylethylketon in einem Volumenanteil (v%) von 25%
• 4. Thermoplastisches Harz 2: Ethylen-Vinylacetatcopolymer (EVA 700, Byer) gelöst in Toluen/Methylethylketon in 40 v%
• 5. Acrylcopolymer: Acrylharz mit einem mittleren Molekulargewicht von 90.000 bis 120.000 g/Mol (AOF7003, Aekyung Chemical) gelöst in Toluen/Methylethylketon in 40 v%
• 6. Radikalisch polymerisierbare Verbindung: Epoxyacrylatpolymer (SP1509, Showa Highpolymer)
• 7. Organisches Peroxid: Benzoylperoxid
• 8. Epoxidharz 1: BPA Epoxidharz (Kukdo Chemical)
• 9. Epoxidharz 2: Epoxidharz enthaltend polyzyklisch aromatische Ringe (HP4700, Dainippon Ink und Chemicals)
• 10: Silica: Nano-silica (R972, Degussa)
• 11. Latentes Härtungsmittel: Mikro-verkapseltes Imidazol (HX3941HP, Asahi Kasei)
• 12. Leitender Partikel 1: Nickel-überzogene Kupferpartikel mit einer Größe von 5 µm
• 13. Leitender Partikel 2: Silver-überzogener Kupferpartikel mit einer Größe von 5 µm

Details of the components used in Examples 1 to 6 and Comparative Examples 1 to 6 are as follows.

• 1. Urethane-modified acrylate resin 1: Synthesized using 60% by weight of polyol (polytetramethylene glycol), 39.97% by weight of three components containing 1,4-butanediol, toluene diisocyanate and hydroxyethyl methacrylate, and 0.03% by weight % Dibutyl tin dilaurate as a catalyst. First, polyol, 1,4-butanediol, and toluene diisocyanate are reacted to synthesize an isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer was further reacted with hydroxyethyl methacrylate to prepare a polyurethane acrylate resin so that the molar ratio of hydroxyethyl methacrylate / isocyanate-terminated prepolymer became 0.5. The reaction was carried out by polyaddition at 90 ° C. and a pressure of 1 atm for 5 hours in the presence of dibutyltin dilaurate as a catalyst, whereby polyurethane acrylate having an average molecular weight of 25,000 g / mol was synthesized.
• 2. Urethane-modified acrylate resin 2: Synthesized using 60% by weight of polyol (polytetramethylene glycol), 39.97% by weight of three components containing 1,4-butanediol, toluene diisocyanate and hydroxyethyl methacrylate, and 0.03% by weight % Dibutyl tin dilaurate as a catalyst. First, polyol, 1,4-butanediol, and toluene diisocyanate are reacted to synthesize an isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer was further reacted with hydroxyethyl methacrylate to produce a polyurethane acrylate resin, the hydroxyethyl methacrylate / isocyanate-terminated prepolymer having a molar ratio of 1. The reaction was carried out by polyaddition at 90 ° C. and a pressure of 1 atm for 5 hours in the presence of dibutyltin dilaurate as a catalyst, whereby polyurethane acrylate having an average molecular weight of 28,000 g / mol was synthesized.
• 3. Thermoplastic resin 1: acrylonitrile butadiene copolymer (1072CGX, Zeon Chemicals) dissolved in toluene / methyl ethyl ketone in a volume fraction (v%) of 25%
• 4. Thermoplastic resin 2: ethylene-vinyl acetate copolymer (EVA 700, Byer) dissolved in toluene / methyl ethyl ketone in 40% by volume
• 5. Acrylic copolymer: acrylic resin with an average molecular weight of 90,000 to 120,000 g / mol (AOF7003, Aekyung Chemical) dissolved in toluene / methyl ethyl ketone in 40% by volume
• 6. Radically polymerizable compound: epoxy acrylate polymer (SP1509, Showa Highpolymer)
• 7. Organic peroxide: Benzoyl peroxide
• 8. Epoxy resin 1: BPA epoxy resin (Kukdo Chemical)
• 9. Epoxy resin 2: Epoxy resin containing polycyclic aromatic rings (HP4700, Dainippon Ink and Chemicals)
• 10: Silica: Nano-silica (R972, Degussa)
• 11. Latent curing agent: micro-encapsulated imidazole (HX3941HP, Asahi Kasei)
• 12. Conductive Particle 1: Nickel-plated copper particles with a size of 5 µm
• 13. Conductive Particle 2: Silver-coated copper particle with a size of 5 µm

Examples 1 to 6 and Comparative Examples 1 to 6

The components were mixed according to the proportions by weight listed in the compositions in Tables 1 and 2, and dissolved and dispersed in an organic solvent using a planetary mixer. The mixture was coated on a peeled PET film, and the solvent was dried for 5 minutes using a convection oven heated to 60 ° C, thereby producing two types of conductive films 25 µm and 35 µm in thickness, respectively. Table 1 Parts by weight example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Urethane - modified acrylate resin 1 40 40 40 40 30th 30th Urethane - modified acrylate resin 2 30th 30th 20th 20th 20th 20th Thermoplastic resin 1 10 10 10 10 10 - Thermoplastic resin 2 - - - - - 10 Acrylic copolymer - - 10 10 20th 20th Radically polymerizable 15th 15th 15th 15th 15th 15th Compound organic peroxide 2 2 2 2 2 2 Epoxy 1 - - - - - - Epoxy 2 - - - - - - Silica - - - - - - Hardening agents - - - - - - Conductive Particle 1 3 - 3 - 3 3 Conductive particle 2 - 3 - 3 - - total 100 100 100 100 100 100 Table 2 Parts by weight Comparative examples 1 2 3 4th 5 6th Urethane - modified acrylate resin 1 35 35 40 - - - Urethane - modified acrylate resin 2 - - 45 - - - Thermoplastic resin 10 - - 40 - - Thermoplastic resin - 10 - 10 - - Acrylic copolymer 35 35 - 30th - - Radically polymerizable 15th 15th 10 15th - - Compound organic peroxide 2 2 2 2 - - Epoxy 1 - - - - 30th 30th Epoxy 2 - - - - 20th 20th Silica - - - - 7th 7th Hardening agents - - - - 40 40 Conductive Particle 1 3 3 3 3 3 3 Conductive particle 2 - - - - - - total 100 100 100 100 100 100

Test to evaluate the properties

To measure the reliability of the connection, each of the connection films prepared in Examples 1 to 6 and Comparative Examples 1 to 6 with a thickness of 25 µm was cut into strips with a width of 1 mm and a length of 15 cm, and each piece (connection film 45 in 4th ) was attached to an electrically conductive electrode on a crystalline silicone cell (electrically conductive electrode 41 on a silicon substrate 43 in 4th ) attached, over one side with a length of 158 mm, at 80 ° C and 1 MPa for 2 seconds. After removing the PET film, a rectangular solder-clad copper wire (1.5 mm in width, 0.2 mm in height and 180 mm in length) was placed on the connection film (wire 42 on connection film 45 in 4th ) and thermally pressed at 150 ° C and 1 MPa for 5 or 3 seconds, whereby a sample for measuring the reliability of the connection was prepared.

To conduct a tensile test and measure a modulus of elasticity, each of the compound conductive films with a thickness of 35 µm was placed on a heating press and silicone rubber with a thickness of 0.2 mm was spread thereon, followed by thermal pressing at 190 ° C and 30 ° C MPa for 15 minutes to cure the bonding film. Then, after removing the release film, the conductive film was cut into samples having a width of 2 mm and a length of 3 mm for tensile test and samples having a width of 5 mm and a length of 30 mm for measuring elastic modulus.

Although the modulus of elasticity can be measured from the stress-strain diagram, it was measured using a dynamic mechanical analyzer (DMA) because a slope of an elastic strain area in a straight line area is apt to vary depending on a person who determines this straight line area, to change.

Furthermore, after curing, the proportion of reactivity of a vinyl group was measured by means of differential scanning calorimetry (DSC) in order to determine whether the samples in question had cured through and through.

Each test was carried out as follows.

• Tensile test

The tensile strength was measured using a universal testing machine (UTM, H5KT, Hounsfield) and the test was carried out as follows.

1) After attaching a 100 N load cell, 2) a holder for performing the measurement was installed, and 3) a sample was snapped into the holder, whereby the tensile elongation was measured at a tensile test speed of 50 mm / min. The yield strength is defined as the stress at which the specimen begins to deform plastically instead of elastically.

• DMA for the modulus of elasticity

The elastic modulus for the cured sample was measured using a dynamic mechanical analyzer (TA Instruments). A sample to be measured was cured using a hot press, and the thorough cure was determined using a DSC. The elastic modulus of the sample was observed at 25 ° C while raising the temperature by 10 ° C / min from -40 to 200 ° C.

• DSC for the reactivity component

The proportion of reactivity was measured by means of a differential scanning calorimeter which is a Perkin-Elmer Diamond DSC.

A predetermined amount of the sample to be measured was collected, and the reactivity ratio of the sample was calculated by finding a calorific value while increasing the temperature by 10 ° C / min from 50 to 220 ° C. Since the reactivity component represents a value from the relative comparison with the sample before curing, the ACF calorific value of the same material was necessarily measured. $$\begin{array}{l}\text{Degree of hardness}\left(\%\right)=100\times \{\text{Standard ACF}\Delta \text{H}\left(\text{J}/\text{G}\right)-\Delta \text{H}\left(\text{J}/\text{G}\right)\text{the one to be measured}n\\ \text{sample}\}/\text{Standard ACF}\Delta \text{H}\left(\text{J}/\text{G}\right)\end{array}$$

• Resistance and functionality (see Fig. 6)

The contact resistance of a sample bonded using ACF as shown in 4th is shown - as in 6th is shown - measured to determine whether the sample is conductive. The contact resistance was measured using a 2000 multimeter (Keithley) with an applied test current of 1 mA (see Multimeter 56 in 6th ) measured. First, the initial contact current of the sample was measured, and the contact current of the sample under high temperature and high humidity conditions or under thermal shock for evaluating the operability was measured.

When measuring under high temperature and high humidity conditions, a change in contact resistance was observed at 85 ° C and 85% RH for a certain period of time. When measuring The contact resistance was measured under temperature shock to evaluate the functionality at a changing temperature from -40 to 100 ° C. The measurement was set up in such a way as to limit a process for raising the temperature from -40 to 100 ° C and then reducing it to -40 ° C within 1 hour, so that each cycle took one hour.

Test results

As shown in Tables 3 and 4, the compound material of the present invention includes at least one vinyl group comprising peroxide which generates free radicals by heat and controls the reaction rate using the peroxide to thereby reduce the contact time by 5 seconds, particularly 3 seconds. to lower. In addition, the joining material has hardening material properties such as an elastic modulus ranging from 10 to 500 MPa at 25 ° C, a tensile elongation of 100% or more, and a yield stress of 10% or more in a stress-strain diagram. Therefore, the connection material of the invention ensures excellent connection performance (while maintaining contact resistance) in connection of the conductive electrode on the cell and the tape. As shown in Table 4, the joining material of Comparative Examples 1, 2 and 4 has inferior contact resistance due to the significant increase in contact resistance after 1000 hours at 85 ° C / 85% RH and after 1000 cycles at -40 ° C / 100 ° C compared to the initial contact resistance. Further, when the polymer resin contains only a urethane-modified acrylate resin in Comparative Example 3, the bonding material has poor contact resistance due to the significant increase in contact resistance after 1,000 hours at 85 ° C / 85% RH and after 1000 cycles at -40 ° C / 100 ° C compared to the initial contact resistance.

Meanwhile, as is apparent from Comparative Example 5, when the epoxy bonding material does not have satisfactory material properties after curing, it causes bonding operability, but has a long bonding time of 10 seconds and inferior performance. Further, as can be seen from Comparative Example 6, it does not offer adequate operability even if the epoxy bonding material is bonded for a short bonding time. Table 3 example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Connection conditions (° C-sec-MPa) 150-5-1 150-3-1 150-5-1 150-3-1 150-5-1 150-5-1 Young's modulus (MPa) 45 45 300 300 400 450 Tensile elongation (%) 280 280 220 220 135 150 Yield strength stress (%) 17th 17th 12th 12th 13th 15th Initial volume resistance (Ω) 0.02 0.02 0.02 0.02 0.02 0.02 Contact resistance after 1,000 hours at 85 ° C / 85% RH (Ω) 0.02 0.02 0.02 0.02 0.02 0.02 Contact resistance at 1,000 cycles at -40 ° C / 100 ° C (Ω) 0.02 0.02 0.02 0.02 0.02 0.02 Table 4 Comparative example 1 2 3 4th 5 6th Connection conditions (° C-sec-MPa) 150-5-1 150-5-1 150-5-1 150-5-1 190-10-1 190-5-1 Young's modulus (MPa) 1000 50 5 78 1300 1300 Tensile elongation (%) 24 65 350 210 5 5 Yield strength stress (%) 7th 8th 20th No No 1 No Beginner 0.02 0.02 0.02 Yield strength 0.02 Yield strength 0.02 Yield strength 0.02 Volume resistance (Ω) Contact resistance after 1,000 hours at 85 ° C / 85% RH (Ω) 1.3 10> 10> 0.21 0.02 10> Contact resistance at 1,000 cycles at - 40 ° C / 100 ° C (Ω) 10> 10> 10> 1.8 0.02 10>

The bonding material according to the present invention can improve the adhesive force and functions properly when it is used excluding a bus bar in the current collecting electrode or as a 20 µm to 1 mm thin wire. In this case, since the current collecting electrode performs the same function as the conductive particle in the bonding material, the non-conductive adhesive film can be used excluding the conductive particle.

Although the aforementioned embodiments of the present invention have been described with reference to the underlying drawings and tables, the present invention is not limited to these embodiments and can be embodied in many different forms. Those skilled in the art will appreciate that the present invention can be used otherwise than expressly described without changing the technical spirit or essential features of the present invention. It is therefore to be understood that the embodiment is to be considered in all aspects as illustrative and not in a restrictive sense.

Claims (12)

An electrical connection material between conductors, comprising 40% by weight to 80% by weight of a urethane-modified acrylate resin, the connection material comprising a polymer binding resin, a free-radically polymerizable compound, organic peroxide, and a conductive particle, the polymer binding resin a urethane-modified acrylate resin and at least one copolymer selected from an acrylonitrile-butadiene copolymer, an ethyl vinyl acetate copolymer and an acrylic copolymer, and wherein the connecting material has a tensile elongation of 100% to% 500% after curing; and - a yield point load of ≥10% to ≤50% in a stress-strain diagram, and / or - has a modulus of elasticity of ≥10 MPa to ≤500 MPa at 25 ° C. An electrical connection material between conductors according to Claim 1 , comprising 40% by weight to 80% by weight of a urethane-modified acrylate resin, and having a tensile elongation of 100% to 500% and a modulus of elasticity after curing of 10 MPa to 500 MPa at 25 ° C. The electrical connection material according to Claim 1 or 2 , wherein the connecting material has a tensile elongation of ≥200% to ≤300% after curing. The electrical connection material according to the Claims 1 to 3 where the bonding material is ≥70% by weight to ≤85% by weight of the polymer binding resin, ≥13% by weight to ≤20% by weight of the free-radically polymerizable compound, ≥1% by weight to ≤5% by weight of the organic peroxide, and 1 1% by weight to 5% by weight of the conductive particle. The electrical connection material according to the Claims 1 to 4th wherein the polymer binding resin comprises 60% by weight to 90% by weight of the urethane-modified acrylate resin and 10% by weight to 40% by weight of the copolymer. The electrical connection material according to the Claims 1 to 5 , wherein the acrylic copolymer has a glass transition temperature of ≥50 ° C to ≤120 ° C. The electrical connection material according to the Claims 1 to 6th wherein the acrylic copolymer has an acidity of ≥1 mgKOH / g to ≤100 mgKOH / g. The electrical connection material according to the Claims 1 to 7th wherein the free-radically polymerizable compound has at least one monomer selected from the group consisting of urethane (meth) acrylates, epoxy (meth) acrylates, polyester (meth) arylates, fluoro (meth) acrylates, fluorene (meth) acrylates, silicone (meth) acrylates , Phosphorus (meth) acrylates, maleimide-modified (meth) acrylates, acrylate (methacrylates), and (meth) acrylate monomers. The electrical connection material according to the Claims 1 to 8th wherein the organic peroxide comprises at least one selected from the group of ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters, and peroxycarbonate. The electrical connection material of the Claims 1 to 9 wherein the conductive particle comprises at least one selected from metallic particles containing Ni, Pd, Cu, Ag, Al, Ti, Cr or mixtures thereof, and conductive particles produced by coating non-conductive particles with the above metal particles. Use of the electrical connection material according to one of the Claims 1 to 10 In a solar cell module comprising a plurality of solar cells connected via an interconnection structure, the interconnection structure comprises: at least one electrode on a surface of each solar cell; a conductive wire connected to the electrodes on the plurality of solar cells; and an electrical connection material according to the Claims 1 to 10 between the conductive wire and each of the electrodes, the electrical connection material comprises a polymer bonding resin, a radical polymerizable compound, organic peroxide, and a conductive particle, wherein the polymer bonding resin is ≥40% by weight to ≤80% by weight of a urethane-modified Acrylate resin and at least one copolymer selected from an acrylonitrile-butadiene copolymer, an ethyl vinyl acetate copolymer and an acrylic copolymer, based on a total weight of the electrical connection material, and after curing has a tensile elongation of ≥ 100% to ≤ 500% and a Yield stress of ≥ 10% to ≤ 50% in a stress-strain diagram. Use after Claim 11 , wherein the electrical connection material is on a copper conductor, the copper conductor comprises on one of its surfaces at least one metal from copper, stainless copper or tin, solder, silver, and nickel.

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